fix NaN assertions that never fired due to IEEE 754 NaN comparison

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: chongchonghe

src/problems/ParticleSink/testParticleSink.cpp

@@ -168,7 +168,7 @@ auto problem_main() -> int
 	pp.query("refine_half_domain", refine_half_domain);
 	double boost_vel_x = NAN;
 	pp.query("boost_vel_x", boost_vel_x);
-	AMREX_ASSERT_WITH_MESSAGE(boost_vel_x != NAN, "boost_vel_x must be set in the input file");
+	AMREX_ASSERT_WITH_MESSAGE(std::isfinite(boost_vel_x), "boost_vel_x must be set in the input file");
 
 	// Problem initialization
 	QuokkaSimulation<SinkProblem> sim;

src/radiation/radiation_system.hpp

@@ -1018,10 +1018,10 @@ AMREX_GPU_DEVICE auto RadSystem<problem_t>::ComputeRadPressure(const double erad
 		Tnz = T[2][2];
 	}
 
-	AMREX_ASSERT(Fn != NAN);
-	AMREX_ASSERT(Tnx != NAN);
-	AMREX_ASSERT(Tny != NAN);
-	AMREX_ASSERT(Tnz != NAN);
+	AMREX_ASSERT(std::isfinite(Fn));
+	AMREX_ASSERT(std::isfinite(Tnx));
+	AMREX_ASSERT(std::isfinite(Tny));
+	AMREX_ASSERT(std::isfinite(Tnz));
 
 	RadPressureResult result{};
 	result.F = {Fn, Tnx * erad, Tny * erad, Tnz * erad};